Nitrite treatment of nickel catalyst to prevent nuclear hydrogenation in reduction of anthraquinones



United States Patent TREATMENT OF NICKEL CATALYST TO PREVENT NUCLEARHYDR OGENATION IN RE- DUCTION 0F ANTHRAQUINONES Robert Umhoefer,Kenmore, N. Y., assignor, by mesne assignments, to Food Machinery andChemical Corporation, San Jose, Calif., a corporation of Delaware NoDrawing. Application August 21, 1952, Serial No. 305,711

Claims. (Cl. 260--369) This invention pertains to hydrogenationcatalysts and more particularly to a selectively acting nickelhydrogenation catalyst suitable for the production of hydroquinones fromquinones.

If quinones, such as naphthoquinones, anthraquinones, phenanthraquinonesand other quinones, are hydrogenated using Raney nickel catalyst, thecorresponding hydroquinones will form very easily, but the reaction isapt to proceed further, leading to nuclear hydrogenation with theformation of tetrahydro-hydroquinones. Thus, when hydrogenating2-ethylanthraquinone in the presence of Raney nickel, the reaction willnot stop with the formation of the desired 2-ethylanthrahydroquinone,but will proceed to tetrahydro-Z-ethylanthraquinone.

It is an object of this invention to provide means to prevent nuclearhydrogenation when catalytically hydrogenating quinones.

It is a further object of this invention to produce a treated nickelcatalyst that is inactive for hydrogenation of the nucleus and activetoward the hydrogenation of quinones to hydroquinones.

In my co-pending application, Serial No. 278,739, filed March 26, 1952,the use of amines to treat the nickel catalyst to prevent nuclearhydrogenation has been described. I have now found that by treating thenickel catalyst with a nitrite, the ability of the catalyst tohydrogenate the nucleus is greatly reduced or even completely inhibited,without impairment of its ability to hydrogenate the quinones to thecorresponding hydroquinones. Moreover, the effect of the treatment ofthis invention is a relatively lasting one.

In accordance with my invention, the nickel catalyst, prior to its usein the hydrogenation reaction, is treated with a nitrite.

The following examples will serve to further illustrate the principle ofmy invention.

Example I A Raney nickel catalyst was used to cause hydrogenation of 0.8g. of Z-ethyIanthraquinone dissolved in 20 ml. of a solvent mixtureconsisting of equal parts of ethylbenzene and tributyl phosphate. Thequinone was shaken in this mixture with the Raney nickel catalyst at 30C. under a hydrogen pressure of 750 mm. Hydrogen was absorbed at a ratecorresponding to 62 mL/minutes/ gram during the formation ofZ-ethyIanthrahydroquinone. After all the quinone had reacted in thismanner, hydrogen absorption continued at a rate corresponding to 0.59mL/minute/ gram with the formation of the corresponding amount oftetrahydro-2-ethylanthrahydroquinone, this second hydrogenation stepcorresponding to nuclear hydrogenation.

Example II Another sample of the same Raney nickel catalyst as used inExample I was treated with an equal volume of iso-propylalcohol in whichwas dissolved 2% of isoamylnitrite calculated on the weight of thecatalyst. The

2,720,531 Patented Oct. 11, 1955 Example III Another sample of the sameRaney nickel catalyst as used in Example I was treated with an equalvolume of iso-propylalcohol in which was dissolved 2% of butylnitritecalculated on the weight of the catalyst. The catalyst was mixed withthe butylnitrite solution and left standing for 24 hours at roomtemperature. The required volume of catalyst was then withdrawn from themixture and used in the same manner as described in Example I tohydrogenate 0.8 g. of 2-ethylanthraquinone. After the quantity ofhydrogen necessary for the formation of 2- ethylanthrahydroquinone hadbeen absorbed, no further uptake in hydrogen occurred, indicating thatnuclear hydrogenation was completely prevented.

In all these experiments, hydroquinone formation was not impaired assubstantially stoichiometric amounts of hydrogen necessary forhydroquinone formation from the quinone were absorbed.

The above examples, it will be understood, are given to illustrate theprinciples of the invention only, as the treatment of the porous nickelcatalyst of the Raney type to restrict the action of hydrogen toreduction of the quinone group to hydroquinone and prevent nuclearhydrogenation, is effective upon the employment of organic nitrites,particularly the aliphatic nitrites of less than 8 carbon atoms, as forinstance, iso-amylnitrite or butylnitrite. The treatment is simple inoperation, and generally comprises contact of the catalyst with thenitrite, as for instance, by impregnation, the nitrite preferably beingcarried in solution in a suitable solvent or a small quantity of thenitrite may be included in the quinone.

The preferred method of treating the catalyst is to immerse the same inand agitate it with the solution of the nitrite to obtain eifectiveabsorption of the catalyst, which operation may be performed at roomtemperature. In performing the treatment in this manner, excesssolutions may be readily removed from the catalyst by simple filtrationor other conventional separation procedure, the impregnated and treatedcatalyst being immediately ready for use in the hydrogenation reaction.

In Serial No. 278,739, filed March 26, 1952, there is described thetreatment of nickel catalysts of the Raney type with amines in order toinduce selective hydrogenation of the quinones and to prevent nuclearhydrogenation thereof. It is believed that the nitrites described hereinas effective catalyst protectors are probably reduced, and in suchreduced state cause the catalyst selectively to act in the hydrogenationprocess. In any event, the nitrite group, rather than the hydrocarbon towhich it is attached, is the active agent in the protective action.

What is claimed is:

1. In the process of hydrogenating anthraquinones dissolved in liquidphase in the presence of a. nickel catalyst, the method of preventingnuclear hydrogenation which comprises carrying out the reaction in thepresence of an organic nitrite.

2. In the process of hydrogenating anthraquinones dissolved in liquidphase in the presence of a nickel catalyst, the method of preventingnuclear hydrogenation which comprises treating the nickel catalyst priorto its use with an organic nitrite, and carrying out the reaction in thepresence of the so-treated catalyst.

3; In the process of hydrogenating authraquinones dissolved in liquidphase in the presence of a nickel catalyst, the method of preventingnuclear hydrogenation which comprises treating the nickel catalyst priorto its use with iso-amylnitrite.

4. In the process of hydrogenating anthraquinones dissolved in liquidphase in the presence of a nickel catalyst, the method of preventingnuclear hydrogenation which comprises treating the nickel catalyst priorto its use with butylnitrite.

5. In the process of hydrogenating anthraquinones dissolved in liquidphase in the presence of a nickel catalyst,

4 the method of preventing nuclear hydrogenation which comprisestreating the nickel catalyst prior to its use with and aliphatic nitriteof less than 8 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTSHannion et al. Jan. 24, 1950 OTHER REFERENCES Anisimov et al.: Chem.Abstracts, 32 col. 5773 (1938), 1 page.

1. IN THE PROCESS OF HYDROGENATING ANTHRAQUINONES DISSOLVED IN LIQUIDPHASE IN THE PRESENCE OF A NICKEL CATALYST, THE METHOD OF PREVENTINGNUCLEAR HYDROGENATION WHICH COMPRISES CARRYING OUT THE REACTION IN THEPRESENCE OF AN ORGANIC NITRITE.